Concepts

There are three user statuses:

• Running in the foreground (Online)
• Running in the background (PushOnline)
• Not logged in (Offline)

Note：

The PushOnline status exists only on mobile clients (Android/iOS) and does not exist on PC or web clients.

Running in the foreground (Online)

The Online status means that a smooth TCP connection is maintained between the client and the IM server. In this condition, the client can send messages to the IM server and receive messages from it.

When a user opens an app, the status is Online.

When an app starts, a TCP persistent connection is established between the client and the IM server. The IM server saves the online information of clients, such as network links, platforms, and versions. When the app is running, the IM SDK regularly sends heartbeats to confirm the online status of the user.

Note：

Heartbeat: every two minutes, the IM SDK sends a heartbeat packet to the server to confirm the online status of the user.

Running in the background (PushOnline)

When a client is in the PushOnline status, the TCP persistent connection between the client and the IM server is disconnected. In this case, messages pushed offline can be received.
In the following scenarios, the user’s status is PushOnline:

• After using an app, the user switches the app to the background, and then the app process is killed by the mobile phone operating system (OS) or the user directly kills the app process.
  If the app is in the keep-alive allowlist of the mobile phone OS, the OS will not kill the app process after the user switches the app to the background. In this case, the status is still Online. One criterion for distinguishing between Online and PushOnline is whether the app process is killed, that is, whether the TCP persistent connection between the client and IM server is disconnected.
• The user disconnects the client from the network (for example, by enabling the airplane mode on the mobile phone) or the client’s network is completely unavailable (for example, when the user enters a tunnel).
  In such circumstances, the client cannot even send TCP FIN or RST packets, and it will take 400 seconds before the heartbeat packet times out. After that, the user’s status will change to PushOnline.

Note：

The PushOnline status exists only on mobile clients (Android/iOS), not on PC, Mini Program, and web clients.

Not logged in (Offline)

Offline refers to the status before a user enters the account and password for login. In this case, the user cannot receive online and offline message pushes.
In the following scenarios, the user’s status is Offline:

• The user logs out or has not logged in to the app since downloading it.
• The user does not log in again within 7 days after the user’s status changes to PushOnline. In this case, the status changes to Offline.

Querying the Online Status of Users

The app backend can query the online status of multiple users via the v4/openim/querystate RESTful API.
Currently, the IM SDK cannot get the online status of users.

User Online Status Change Notifications

IM can notify the app backend of user login and logout events. For more information, see Status Change Callback.

Real-Time Perception of Status Changes

Android, iOS, and PC

In most cases, the changes of user status can be perceived in real time. For example:

• When a user logs in, the user’s status changes to Online.
• When a user logs out, the user’s status changes to Offline.
• When a user kills the client process or when a user switches the app to the background and the client process is killed by the mobile phone OS, the user’s status changes to PushOnline.

In the following special case, it will take 400 seconds before the heartbeat times out. After that, the IM CVM instance can perceive the status change:
When the network is completely unavailable and the client cannot even send TCP FIN or RST packets, it will take 400 seconds before the heartbeat times out. After that, the IM CVM instance can perceive that the user’s status changes to PushOnline. This commonly occurs when the user disconnects the client from the network (for example, by enabling the airplane mode on the mobile phone) or the user enters a tunnel with no network signal.

Web

When a user logs in on the web client, the IM CVM can perceive in real time that the user’s status changes to Online.
When a user’s network is unavailable or when a user directly closes the web page, it will take 400 seconds before the heartbeat times out. After that, the IM CVM can perceive that the user’s status changes to Offline.

Multi-Device Login

Force offline

By default, the IM SDK does not allow multi-device login (for example, simultaneous login on a PC and an Android device). Instead, it forces the previous online device to go offline and allows only the last logged-in device to stay online. For more information on the force offline logic, see:

• Initialization (Android)

Multi-device online

You can modify the multi-device login policy in the IM console to allow users to stay online simultaneously on a PC and mobile phone, or on a PC, iOS device, and Android device. When multi-device login is enabled, users can stay online simultaneously on different devices with different platforms, but not on devices with the same platform. For example, simultaneous login on two iOS devices will trigger force offline.